Controlling method for clothes dryer

ABSTRACT

A controlling method for a dryer is applied to a dryer, in which at least one of a heat pump system and a heater is selected as a heat source for heating air supplied in to a drum and a heat supply capacity of the heat pump system is more than that of the heater. The controlling method includes, when both the heat pump system and the heater are selected as the heat sources, turning the heat pump system on, turning the heater on after the heat pump system is normally turned on, turning the heater off to cool the drum and terminate drying after the drying is performed, and turning the heat pump system off after the heater is turned off.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a Continuation Application of prior co-pending U.S.patent application Ser. No. 14/007,217, filed Sep. 24, 2013, which is aU.S. National Stage Application under 35 U.S.C. §371 of PCT ApplicationNo. PCT/KR2012/002221, filed Mar. 27, 2012, which claims priority toKorean Patent Application No. 10-2011-0028387, filed Mar. 29, 2011, andKorean Patent Application No. 10-2012-0023032, filed Mar. 6, 2012, whoseentire disclosures are hereby incorporated by reference.

BACKGROUND

1. Field

The present disclosure relates to a controlling method for a clothesdryer capable of drying clothes and the like, and more particularly, acontrolling method for a clothes dryer capable of enhancing energyefficiency and reducing a drying time so as for the dryer to operate inan efficient and stable manner, by virtue of using at least one of aheat pump system and a heater as a heat source for heating up air fordrying a target to be dried.

2. Background

In general, a clothes processing apparatus having a drying function,such as a washing machine or a clothes dryer, is an apparatus in whichclothes (laundry, etc.), which have completely washed and thendehydrated, are introduced into a drum and hot air is supplied into thedrum to evaporate moisture contained in the clothes so as to dry theclothes.

As one example, a clothes dryer includes a drum rotatably installedinside a main body for accommodating clothes therein, a driving motorfor driving the drum, a ventilation fan for blowing air into the drum,and a heating unit for heating up air introduced into the drum. Theheating unit may be a type of heater, which uses electric resistanceheat of high temperature generated by electrical resistance or heat ofcombustion generated by burning gas.

Meanwhile, air exhausted from the drum becomes hot humid air due tocontaining moisture from the clothes within the drum. Here, depending ona method of treating such hot humid air, dryers may be classified, forexample, into a circulating type dryer, in which hot humid aircirculates without being exhausted outside the dryer to cool air belowdew-point temperature through a heat exchanger, and accordingly moisturecontained in the hot humid air is condensed to be resupplied, and anexhausting type dryer, in which hot humid air passing through the drumis exhausted directly to the outside.

For the circulating type dryer, in order to condense air discharged outof the drum, air should be cooled below the dew-point temperature andheated by the heating unit prior to being resupplied into the drum.Therefore, when a heater is employed as the heating unit, a heatexchanger for condensing hot humid air discharged out of the drum isseparately needed, and thereby thermal energy supplied by the heater israther discharged to the outside due to heat exchange with the heatexchanger. This structure has an advantage of supplying thermal energyas much as being necessary by use of the heater but causes a problem oflowering thermal efficiency and increasing energy consumption. Also, forair circulation, moisture should be removed sufficiently, which causesthe heat exchanger to be larger in volume and a drying time to belonger.

For the exhausting type dryer, hot humid air should be exhausted to theoutside and external air of room temperature should be introduced andheated up to temperature as high as being required by means of a heatingunit. When a heater is employed as a heating unit in the exhausting typedryer, it has advantages of not separately needing a heat exchanger andreducing a drying time by supplying thermal energy as much as beingrequired by use of the heater. However, the hot air discharged to theoutside is discharged directly to the outside with containing thermalenergy transferred by the heating unit, thereby lowering thermalefficiency and increasing energy consumption.

Therefore, in recent time, a dryer, which is configured such thatnon-used energy is recollected from air discharged out of the drum andreused for heating air supplied into the drum so as to enhance energyefficiency, is being introduced. An example of such dryer is a dryerhaving a heat pump system. The heat pump system includes two heatexchangers, a compressor and an expander (expansion apparatus). With theconfiguration of the heat pump system, a refrigerant which circulates inthe system recollects energy contained in hot air exhausted and therecollected energy is used to heat air supplied into the drum, therebyenhancing the energy efficiency.

In detail, the heat pump system includes an evaporator at an exhaustside from the drum and a condenser at an inlet side of the drum.Accordingly, a refrigerant absorbs thermal energy through the evaporatorand then is pressurized by a compressor to be a refrigerant of hightemperature and high pressure. Afterwards, the thermal energy containedin the refrigerant is transferred to air, which is introduced into thedrum, through the condenser, which allows hot air to be generated byusing the energy which is wasted.

However, when the heat pump system is applied to a dryer, a performanceof the system depends on capacities of an evaporator for absorbingthermal energy and a condenser for discharging energy, and a capacity ofa compressor for compressing a refrigerant. Hence, it is ideal to designthe heat pump system based on required thermal energy, but sizes orcapacities of the compressor used in the dryer, and the condenser andthe evaporator serving as heat-exchangers, actually have to be limited.Therefore, when the heat pump system is used as a heating unit forheating air supplied into the drum, it has an advantage in the aspect ofenergy efficiency but has a problem of increasing a drying time due tothe capacity limitation of the heat pump system. In addition, regardingthe characteristic of the heat pump system, an overload may occur in thecompressor the like, resulting in lowered reliability of the heat pumpsystem.

Upon performing a drying operation merely using the heat pump system, aquantity of heat transferred from the condenser to air is insufficientand accordingly a drying time is extended. To overcome such problem, adryer having an auxiliary heater in addition to the condenser heat pumpsystem has been introduced. Accordingly, when heat is not sufficientlysupplied from the condenser due to the heat pump system not reaching anormal state at the beginning of running thereof, the auxiliary heaterruns together with the heater to supply hot air heated up to temperatureappropriate for drying from the initial operation, and also more heat issupplied by the heater even when the heat pump system is in the normalstate, thereby reducing the drying time.

Here, in the circulating type dryer, since air circulates via theevaporator and the condenser, the heat pump system can normally operateonly when temperature and humidity of air when flowing through theevaporator and the condenser are within an appropriate range. That is,when the evaporator fails to sufficiently cool hot air introduced intothe evaporator due to excessively high temperature of the hot air, airhaving temperature over an appropriate range is introduced into thecondenser, thereby lowering a heat transfer performance of thecondenser. Consequently, when the refrigerant flowing through thecondenser is not cooled sufficiently, a liquid refrigerant is introducedinto the compressor or discharge pressure of the compressor isexcessively raised, thereby badly influencing on reliability of thecompressor.

If an auxiliary heater is added to the circulating type dryer having theheat pump system, the temperature of air introduced into the evaporatorincreases much more, which makes it more difficult to prevent anexcessive load from working on the compressor at the beginning ofrunning the heat pump system.

The above references are incorporated by reference herein whereappropriate for appropriate teachings of additional or alternativedetails, features and/or technical background.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 is a schematic view showing an appearance of a dryer inaccordance with one exemplary embodiment;

FIG. 2 is a schematic view showing an inside of the dryer of FIG. 1;

FIG. 3 is a schematic view showing a heat pump system provided in thedryer of FIG. 2;

FIG. 4 if a schematic view showing the heat pump system and operatingloads in the dryer of FIG. 1;

FIG. 5 is a schematic view showing a contact between an air passage ofthe dryer and a heat source;

FIG. 6 is a planar view showing a lower surface of a main body of thedryer;

FIG. 7 is a partially cut-off view for showing the lower surface of themain body shown in FIG. 6;

FIG. 8 is a schematic view showing an electrical connection for controlof the dryer;

FIG. 9 is a flowchart showing a load operation control according toturning on and off a heat source;

FIGS. 10 and 11 are flowcharts showing an initial operation control ofvarious loads of the dryer;

FIG. 12 is a flowchart showing a heater operation control according towhether or not a compressor of a heat pump system normally operates;

FIG. 13 is a flowchart showing another exemplary embodiment of a heateroperation control according to whether or not the compressor of the heatpump system normally operates; and

FIG. 14 is a flowchart showing a process of determining whether or notthe compressor erroneously operates in the exemplary embodiment of FIG.13.

DETAILED DESCRIPTION Disclosure of Invention Technical Problem

Therefore, to obviate those problems, an aspect of the detaileddescription is to provide a dryer capable of enhancing energy efficiencyby using a heat pump system and reducing a drying time by additionallyusing a heater.

Another aspect of the detailed description is to provide a controllingmethod for a dryer capable of enhancing reliability of a heat pumpsystem by efficiently preventing an overload of a compressor even withusing both the heat pump system and a heater.

Solution to Problem

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a controlling method for a dryer, in which at leastone of a heat pump system and a heater is selected as a heat source forheating air supplied in to a drum and a heat supply capacity of the heatpump system is more than that of the heater, the method including, whenboth the heat pump system and the heater are selected as the heatsources, turning the heat pump system on, turning the heater on afterthe heat pump system is normally turned on, turning the heater off tocool the drum and terminate drying after the drying is performed, andturning the heat pump system off after the heater is turned off.

With the configuration, when a heat supply capacity of the heat pumpsystem is greater than that of the heater, such heat supply capacitiesmay be considered in view of turning on and off the heat pump system andthe heater as the heat sources, which may result in stable operations ofloads.

Here, the method may further include running the drum by driving thedriving motor. The running of the drum may be performed by performingreverse rotation and forward rotation of the driving motor in asequential manner, and the turning on of the heat pump system may bestarted after forward rotation of the driving motor.

With the configuration, prior to turning the heat pump system on, thedrum may be run by the driving motor so as to allow loads to besequentially started.

In the meantime, the method may further include determining whether ornot a compressor included in the heat pump system normally operates. Theturning on of the heater may be performed after checking the heat pumpsystem is normally turned on. The determining of whether or not thecompressor normally operates may be performed by comparing a temperaturevariation of a refrigerant having passed through the compressor with apreset reference temperature variation.

With the configuration, in the dryer having the heat pump system and theheater, the heater may be turned on after the normal operation of theheat pump system is checked. That is, when the heater is turned on in astate that the compressor does not normally operate due to an existenceof error, air heated by the heater may flows through the condenser ofthe heat pump system, which may result in erroneous heat transfer in thecondenser. Accordingly, a refrigerant of high temperature may beintroduced into the compressor, thereby further deteriorating the stateof the compressor.

Therefore, the heater may be turned on after checking that thecompressor normally operates, thus to prevent an introduction of arefrigerant of high temperature or a refrigerant in a liquid phase intothe compressor.

Here, those steps may be performed right after the compressor is startedduring the drying operation. That is, when an auxiliary heater is neededto be run even after checking whether the compressor normally operatesat the beginning, the heat may be turned on after checking whether thecompressor normally operates, thereby preventing damage of thecompressor.

Here, whether or not the compressor normally operates may be determinedby measuring discharge pressure of the compressor. That is, if heattransfer is not properly performed in the compressor, the dischargepressure of the compressor may be raised due to the refrigerant of hightemperature. Therefore, the discharge pressure may be checked by use ofa pressure sensor or the like so as to determine whether the compressornormally operates.

Whether or not the compressor normally operates may also be checked bymeasuring a temperature of a refrigerant discharged from the compressor.That is, the temperature of the refrigerant is not high at the beginningof running the compressor, but as the compressor is running to reach itsnormal state, the temperature of the refrigerant increases. Therefore,the temperature of the refrigerant may be detected to check whether thecompressor normally operates according to a temperature variation of therefrigerant. To this end, the determining of whether or not thecompressor normally operates may include measuring a temperature T1 of arefrigerant discharged from the compressor, measuring a temperature T2of the refrigerant discharged from the compressor after a predeterminedtime from the measurement of T1, and determining whether or not thecompressor normally operates according to a difference between T1 andT2.

Here, when the difference value of T2−T1 is greater than a predeterminedvalue, it may be determined that the compressor normally operates. Thestep may further include stopping power supply to the compressor anddisplaying an existence of error on the dryer when the difference valueof T2−T1 is smaller than the predetermined value.

Advantageous Effects of Invention

The present disclosure may have an effect of allowing stable drying bycontrolling a target to be dried not to be damaged even when performingthe drying operation using two different heat sources.

The present disclosure may allow for stably performing the dryingoperation using two different heat sources, so as to efficientlypreventing an overload of the compressor with using both the heat pumpsystem and the heater, thereby enhancing reliability of the heat pumpsystem.

When a heat supply capacity of the heat pump system is greater than thatof the heater, such heat supply capacities may be considered in view ofturning on and off the heat pump system and the heater as the heatsources, which may result in stable operations of loads.

The drying operation may be performed by at least one of two differentheat sources, so as to enhance energy efficiency or reduce a drying timeaccording to a user selection. Consequently, it may provide effects ofreducing energy consumption and increasing user convenience.

Also, a user may convert a drying mode and recognize such conversion ofthe drying mode in simple ways, thereby improving user s convenience.

In addition, a use time of the dryer may be efficiently decided, whichmay result in saving electric charges.

BEST MODE FOR CARRYING OUT THE INVENTION

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided a controlling method for a dryer, in which at leastone of a heat pump system and a heater is selected as a heat source forheating air supplied in to a drum and a heat supply capacity of the heatpump system is more than that of the heater, the method including, whenboth the heat pump system and the heater are selected as the heatsources, turning the heat pump system on, turning the heater on afterthe heat pump system is normally turned on, turning the heater off tocool the drum and terminate drying after the drying is performed, andturning the heat pump system off after the heater is turned off.

MODE FOR THE INVENTION

Embodiments of the present invention will be described below in detailwith reference to the accompanying drawings where those components arerendered the same reference number that are the same or are incorrespondence, regardless of the figure number, and redundantexplanations are omitted. In describing the present invention, if adetailed explanation for a related known function or construction isconsidered to unnecessarily divert the gist of the present invention,such explanation has been omitted but would be understood by thoseskilled in the art. The accompanying drawings are used to help easilyunderstood the technical idea of the present invention and it should beunderstood that the idea of the present invention is not limited by theaccompanying drawings. The idea of the present invention should beconstrued to extend to any alterations, equivalents and substitutesbesides the accompanying drawings.

FIG. 1 is a schematic view showing an appearance of a dryer inaccordance with one exemplary embodiment. As shown in FIG. 1, a dryer100 may include a main body 110 defining an appearance, and a drum 10rotatably installed inside the main body 110 and having a plurality oflifters protruding from an inner circumferential surface. An opening 140through which clothes as a target to be dried are introduced may beformed at a front surface of the main body.

The opening 140 may be opened or closed by a door 130. A control panel120 having a variety of manipulation buttons for operating the dryer anda display unit may be located above the opening 140. A drawer 150 may bedisposed at one side of the control panel 120. The drawer 150 maycontain therein a liquid or the like to be sprayed into the drum.

FIGS. 2 and 3 are schematic views showing an inside of the exemplaryembodiment of FIG. 1. As shown in FIG. 2, the drum 10 may be rotatablyinstalled inside the main body 110 so as for targets to be dried to bedried therein. The drum 10 may be rotatably supported by supporters (notshown) at front and rear sides thereof.

The drum 10 may be connected to a driving motor 20 located at a lowerportion of the dryer via a driving force transfer belt 22 so as toreceive a rotational force from the driving motor 20. A pulley 21 may bedisposed at one side of the driving motor 20 and the driving forcetransfer belt 22 for driving (working, running, rotating) the drum 10may be connected to the pulley 21.

A suction duct 50 may be installed at a rear side of the drum 10, and aheater 40 for heating air sucked may be installed at the suction duct50. The heater 40 may be configured to use electrical resistance heat ofhigh temperature for enhancing efficiency of a space occupied in thedryer. The suction duct 50 may be provided with a discharge opening 51connected to the rear of the drum and allowing heated air to bedischarged into the drum therethrough.

At a lower side of the front of the drum 10 may be installed a filter 65for filtering off foreign materials, such as lint and the like includedin air discharged out of the drum 10, and an exhaust duct 60 throughwhich foreign material-filtered air can be discharged out of the drum10. The suction duct 50 and the exhaust duct 60 may be divided intosuction and exhaust based on the drum 10. Here, FIG. 2 exemplaryillustrates the circulating type dryer, but the present disclosure maynot be limited to the type. Alternatively, the present disclosure may beapplicable to an exhausting type dryer.

A lint filter installation unit 112 for installation of the filter 65into which the air exhausted from the drum 10 is introduced may beformed near the lower portion of the front of the drum 10. The lintfilter installation unit 112 may not only provide an installation spacefor the filter 65 for filtering the lint contained in hot air exhaustedfrom the drum 10 but also define a part of passage through which hot airflows.

In the exemplary embodiment of the circulating type dryer as shown inFIG. 2, the suction duct 50 and the exhaust duct 60 may be integrallyformed with each other so as to define one circulation channel 55.However, in an exemplary embodiment (not shown) for an exhausting typedryer, the suction duct and the exhaust duct may not be connected toeach other.

A ventilation fan 30 for sucking air existing in the drum 10 andforcibly blowing the sucked air may be installed in the exhaust duct 60.For example, for the circulating type dryer of FIG. 2, the exhaust duct60 may serve to induce air, which is forcibly blown by the ventilationfan 30, into the drum 10 via the suction duct 50. On the contrary, forthe exhausting type dryer, the exhaust duct may serve to induce airforcibly blown by the ventilation fan 30 to the outside.

This exemplary embodiment may employ a pull-type ventilation fan, whichexists in a duct for exhausting air out of the drum therethrough so asto suck the air discharged out of the drum toward the exhaust duct.

As aforementioned, at the one side of the driving motor 20 may beprovided the pulley 21 to which the driving force transfer belt 22 fordriving the drum 10 is connected. Here, the other side of the drivingmotor 20 may be connected with a driving shaft of the ventilation fan 30such that the driving motor 20 can drive the ventilation fan 30. Hence,in the exemplary embodiment of FIG. 2, when the driving motor 20rotates, the drum 10 and the ventilation fan 30 rotates simultaneously.

The exemplary embodiment shown in FIG. 3 shows a heat pump system 70which absorbs waste heat from air discharged from the drum inside themain body and supplies the absorbed waste heat to air introduced intothe drum. The exemplary embodiment of FIG. 3 may be a circulating typedryer or an exhausting type dryer.

The heat pump system 70 may construct a thermodynamic cycle by includinga first heat exchanger 71 for absorbing waste heat from air dischargedout of the drum 10, a compressor 72, a second heat exchanger 73 forheating air introduced into the drum, and an expansion valve 74. Thatis, the first heat exchanger 71, the compressor 72, the second heatexchanger 73 and the expansion valve 74 may be connected by pipes in asequential manner.

FIG. 4 shows an example that the heat pump system is mounted in the mainbody of the dryer. As shown in FIG. 4, the first heat exchanger 71 maybe an evaporator based on a refrigerant of the heat pump system, and thesecond heat exchanger 73 may be a condenser. Each of the first heatexchanger 71 and the second heat exchanger 73 may have therein onerefrigerant pipe disposed in a zigzag line. The refrigerant pipe mayhave radiation pins on its surface so as to ensure a sufficient heattransfer area with air.

Here, the evaporator may be the same as or smaller than the condenser inview of a heat exchange capacity. That is, FIG. 4 exemplarilyillustrates that the heat exchange capacity of the evaporator is thesame as that of the condenser. Unlike to the exemplary embodiment shownin FIG. 4, the heat exchange capacity of the evaporator mayalternatively be designed to be smaller than that of the condenser. Thisis for collecting waste heat as much as possible so as to use forheating air introduced into the drum, and also for ensuring reliabilityof the heat pump system by allowing for discharging energy absorbed bythe refrigerant as much as possible through the condenser.

Various types of valves may be employed as the expansion valve 74. Thisexemplary embodiment employs a Linear Expansion Valve (LEV) whoseopening rate is controlled by an electrical signal. That is, acontroller 200 to be explained later may decide the opening rate of thevalve by receiving an input pulse.

FIG. 5 shows an exemplary circulating type dryer, which shows a path ofheating circulated air by the heat pump system and the heater. As shownin FIG. 5, a refrigerant of the heat pump system exchanges heat with hothumid air, which is discharged out of the drum, in an evaporator as thefirst heat exchanger, so as to be in a gaseous state of low temperature.The refrigerant in the gaseous state is then compressed in thecompressor to become a gaseous state of high temperature and highpressure. Afterwards, the refrigerant exchanges heat with cold air,which is to flow into the drum, in a condenser as the second heatexchanger, so as to be in a state of low temperature and high pressure.The refrigerant is expanded in the expansion valve to change into aliquid state of low temperature and low pressure.

Here, with regard to the circulating type dryer, air which has passedthrough the drum becomes hot and humid due to moisture being evaporatedfrom a target to be dried. The hot humid air is then cooled into a lowdry state, which moisture is removed, through the heat exchange in thefirst heat exchanger, so as to be in a state capable of being resuppliedinto the drum. On the contrary, with regard to the exhausting typedryer, air is changed into hot humid air due to moisture beingevaporated from a target to be dried. The hot humid air is then cooledinto a low dry state through the heat exchange in the first heatexchanger, and exhausted to the outside.

The heat pump system 70 includes the evaporator 71, the expansionapparatus 74, the compressor 72 and the condenser 73. Here, theevaporator 71 and the condenser 73 are installed on a circulationchannel 55, and the expansion apparatus 74 and the compressor 72 aredisposed outside the circulation channel 55. Accordingly, while airintroduced from the lint filter installation unit 112 flows along thecirculation channel 55, it flows sequentially via the evaporator 71 andthe condenser 73 so as to be cooled (condensed) and reheated. Moisturecontained in hot air is condensed during a cooling process to form on asurface of the evaporator 71 or be dropped down from the evaporator. Thethusly-generated condensed water is first collected in a condensed watercollecting portion located below the evaporator 71.

As a heat source for heating air introduced into the drum up to hightemperature, at least one of the condenser as the second heat exchangerand the heater 40 may be used. The heated air is introduced into thedrum to dry the target to be dried and then flows down along the frontof the drum. Such air accordingly flows through the exhaust duct via thelint filter.

The suction duct 50 may be installed at the downstream of thecirculation channel 55. The suction duct 50 may be connected to thecirculation channel 55 such that the hot air introduced from thecirculation channel 55 can be resupplied into the drum. In addition, theheater 40 may be installed inside the suction duct 50, so as to reheatthe hot air which has been first heated by the condenser 73. The heater40 may be turned on (run, started, driven) at an initial time when theheat pump system does not reach a normal state to prevent temperature ofhot air from being lowered, or reduce a drying time by additionallyproviding heat even in the state that the heat pump system reaches thenormal state.

Here, the heater may be selectively used. When air is heated only usingthe heat pump system as a heat source, it is excellent in the aspect ofenergy efficiency, but causes a problem of extending the drying time.Therefore, the heater may be used as an auxiliary heat source to reducethe drying time according to a user selection. Alternatively, only theheater may be used as the heat source according to a user selection. Adryer which performs a drying operation by selectively using the heatpump system and the heater may be referred to as a hybrid dryer.

Meanwhile, when the heater is selectively used, the heat pump system mayserve as a main heat source and the heater may serve as an auxiliaryheat source. Here, the heat pump system, as aforementioned, is used asthe main heat source in the aspect of the energy efficiency. In thiscase, a heat supply capacity of the heat pump system as the main heatsource may be configured to be larger than that of the heater. Asaforementioned, since the heat pump system is used as the main heatsource and the heater is used as the auxiliary heat source, energyefficiency can be enhanced by making the heat supply capacity differentaccording to the heat source.

In terms of the configuration, energy which remains unused can becollected from air discharged out of the drum and reused to heat airsupplied into the drum, thereby increasing energy efficiency. Also, theheater as well as the heat pump system can be used as the heat sourcefor heating the air supplied into the drum, which may result inreduction of a drying time.

FIG. 6 is a planar view showing a lower surface of a main body of thedryer, and

FIG. 7 is a partially cut-off view for showing the lower surface of themain body shown in FIG. 6. As shown in FIGS. 6 and 7, a bottom surface113 may be installed at a lower surface of the main body, configure apart of the circulation channel, and provide an installation space forstably supporting the heat pump system. In detail, based on FIG. 6, thecirculation channel in which the evaporator 71 and the condenser 73 areinstalled is disposed at the left side and the expansion valve 74 andthe compressor 72 are installed at the right side.

In addition, the lint filter installation unit 112 may be formed at afront portion (a lower portion in FIG. 6) of the main body and acirculation channel inducing unit 114 may be formed to communicate withthe lint filter installation unit 112. The circulation channel inducingunit 114 communicating with the lint filter installation unit 112 mayinduce hot air exhausted from the drum toward the evaporator 71. To thisend, the circulation channel inducing unit 114 may include a pluralityof guide vanes 114 a for guiding introduced air toward the evaporator71.

The hot air induced by the guide vanes 114 a may be introduced into theexhaust duct 60 or the circulation channel 55. The circulation channel55 may be defined by the bottom surface 113 of the main body, partitionwalls (not shown) on the bottom surface 113, and a cover plate 115 forcovering an upper portion of a space formed by the partition walls. Thatis, the circulation channel 55 is defined by the cover plate 115 and thepartition walls of the bottom surface 113. Air flowing through thethusly-generated circulation channel 55 then flows sequentially via theevaporator 71 and the condenser 73 so as to be introduced into thesuction duct 50 via a suction duct connection portion 50 b formed at arear surface of the main body.

In the meantime, a portion of the bottom surface of the main body, inwhich the evaporator and the condenser are disposed, may serve as acondensed water collecting portion 113 a. That is, the condensed waterwhich is generated due to air being condensed by the evaporator 71 isfirst collected in the condensed water collecting portion 113 a. Thecollected condensed water is then introduced into a condensed waterstoring portion 113 b located adjacent to the compressor 72. Thecondensed water collecting portion 113 a and the condensed water storingportion 113 b may be partitioned by a partition wall which is not shown,and communicate with each other via a through hole formed through thepartition wall.

Accordingly, when a water level of the condensed water collected in thecondensed water collecting portion 113 a is raised over a predeterminedlevel, the condensed water is introduced into the condensed waterstoring portion 113 b via the through hole to be stored therein. Thecondensed water stored in the condensed water storing portion 113 b maythusly be pumped to a control valve 116, which is installed at an upperportion of the cover plate 115, by a pump 90. The control valve 116 maydistribute the condensed water supplied by the pump 90 into respectivewashing nozzles 117 to remove foreign materials such as lint attachedonto the surface of the evaporator 71.

Here, the washing nozzles 117 may not always have to be provided inplurality. It may also be considered to wash the entire evaporator usingone nozzle. Another example of removing such lint using a brush, whichis installed to be movable along the surface of the evaporator, may alsobe considered.

Since the clothes dryer according to the present disclosure uses theheat pump system for maximization of energy efficiency, a refrigeranthas to continuously circulate in the heat pump system. Here, in the heatpump system, heat exchange is generated between a refrigerant and air tobe supplied into the drum by a phase change of the refrigerant. That is,a refrigerant in a liquid phase (liquid state) and a refrigerant in agas phase (gaseous state) coexist on a passage of the refrigerant in theheat pump system.

Here, if heat is not sufficiently supplied from the evaporator, therefrigerant discharged from the evaporator is partially introduced intothe compressor even in the liquid state. When the refrigerant in theliquid state is introduced into the compressor, it may be harmful to thecompressor or lower energy efficiency, thereby causing a problem inreliability of the heat pump system.

Therefore, to detect such state, a temperature difference of arefrigerant having passed through the evaporator may be detected(sensed) so as to indirectly check dryness of the refrigerant. Theexemplary embodiment of FIG. 5 includes a temperature sensor 213installed at an inlet side of the evaporator, and a temperature sensor214 at an outlet side of the evaporator 71 or an inlet side of thecompressor 72.

Also, since the heater can be used as the heat source, heat load isaccumulated in the heat pump system, which may cause an overload of thecompressor 72. Hence, to sense this, it is necessary to measure thetemperature of the refrigerant, respectively, at the inlet side and theoutlet side of the compressor 72 so as to prevent the overload of thecompressor 72. In the exemplary embodiment of FIG. 5, the temperaturesensor 214 may be installed at the inlet side of the compressor 72, anda temperature sensor 215 may be disposed at the outlet side of thecompressor 72. Here, the temperature sensors for the refrigerant may beattached onto a surface of an inlet pipe or discharge pipe connected tothe compressor 72 to indirectly measure the temperature of therefrigerant.

Also, the clothes dryer is to dry a target to be dried, containingmoisture, by supplying hot air, so the target to be dried has to beprotected from damage due to the hot air. Accordingly, a temperature ofthe inlet side of the drum 10 is measured to control air introduced intothe drum 10 not to be overheated, and a temperature of the outlet sideof the drum 10 is measured to control the temperature of the target tobe dried not to be increased because the target to be dried issufficiently dried in the drum 10. Hence, a temperature sensor 211 maybe installed at an inlet side of the drum 10 through which air issupplied into the drum 10, and a temperature sensor 212 may be installedat an outlet side of the drum 10 through which air is discharged fromthe drum 10. Also, a humidity sensor 220 may be installed inside thedrum 10 contactable with the target to be dried so as to preciselycontrol the dryness of the target to be dried, accommodated in the drum10.

In this exemplary embodiment, the temperature sensors 210 (i.e., 211,212, 213, 214 and 215) may preferably be implemented as a thermister.FIG. 8 shows various components electrically connected to a controller.As shown in FIG. 8, the temperature sensors 210 and the humidity sensor220 may be electrically connected to a controller 200 installed in thedryer, thus to provide signals corresponding to measured temperature andhumidity to the controller 200. The controller 200, in turn, controls anamount of refrigerant flowing in the heat pump system 70 by use of theexpansion valve 74, control operations of the compressor 72 of the heatpump system 70 and the heater 40, control the driving motor 20 of thedrum 10 to control the drum 10 and the ventilation fan 30, and control acooling fan 80 to be explained later.

The heat pump system according to the exemplary embodiment shown in FIG.4 may further include a third heat exchanger 75 as a second condenserfor overcooling a refrigerant to appropriately maintain a state of arefrigerant introduced into the expansion valve 74. The refrigerantintroduced into the expansion valve 74 has to be in a liquid phase.However, in some cases, it is introduced in a gas phase and thereby aflow of the refrigerant in the expansion valve 74 may be blocked. Toprevent this problem, the second condenser 75 for overcooling therefrigerant may further be provided. Overcooling the refrigerant by thesecond condenser 75 may also have an effect of preventing an overload ofthe compressor.

A cooling fan 80 may further be provided to enhance efficiency of thesecond condenser 75. The cooling fan 80 may be disposed in the main bodyof the dryer to allow external air to be introduced into the main bodyvia a suction opening 111 formed at the main body. Accordingly, thecooling fan 80 may have not only the functions of enhancing theefficiency of the second condenser 75 and preventing the overload of thecompressor 72, but also a function of cooling the compressor 72 and thelike by allowing the external air to be introduced into the dryer. Thismay result in reduction of an overload of the heat pump system. This mayalso be more efficient when the overload occurs in the compressor 72 inthe hybrid dryer having the heater as another heat source separate fromthe heat pump system. The cooling fan 80 may be controlled by thecontroller 200.

The filter 65 shown in FIG. 3 may filter foreign materials which may becontained in air discharged out of the drum 10. Especially, in the dryerhaving the heat pump system which reuses air discharged from the drum,foreign materials such as lint and the like should be removed by thefilter.

The drying process for a target to be dried, performed by the dryer, asaforementioned, may be regarded as a process of evaporating moisture bysupplying heated air (hot air) into the drum. Here, for the sake ofexplanation, the drying process may be segmented based on dryness of thetarget to be dried.

Performing a drying operation only using the heat pump system as a heatsource for supplying heat into the drum in view of energy efficiency maybe referred to as a normal drying mode. Also, performing a dryingoperation using both the heat pump system and the heater as the heatsource to reduce a drying time with considering the energy efficiencymay be referred to as a high-speed drying mode. In addition, performinga drying operation only using the heater as the heat source may bereferred to as a special drying mode. The terms for the drying modes aremerely specified for convenience of explanation, and used to distinguishthe heat source for heating air supplied into the drum.

In the dryer according to the aforementioned exemplary embodiment, boththe normal drying mode and the high-speed drying mode may be appliedaccording to a user selection. The special drying mode may also beapplied according to the selection.

Each drying mode uses a different heat source, which results indifferent heat energy (thermal energy) supplied per hour, and differentheat load applied to the heat pump system. Hence, a control for the heatsource or the like may differ in each drying mode. This will bedescribed in detail later.

Components disposed in the main body of the dryer are under control ofthe controller 200. The controller 200 may control those componentsbased on measurements received from the temperature sensors and thehumidity sensor.

Meanwhile, the control for the dryer may depend on turning on and off(starting and stopping, initiation and termination, activation anddeactivation) of the heat source. FIG. 9 is a flowchart showingsequential steps of controlling the dryer based on turning on and off ofthe heat source. Especially, in the hybrid dryer using the heat pumpsystem and the heater as the heat source, the sequence of turning on andoff the heat sources may have significance. In addition, in a dryerwhich employs a heat pump system as a main heat source such that a heatsupply capacity of the heat pump system is more than that of the heater,the sequence of turning on and off the heat sources may have asignificant meaning.

As shown in FIG. 9, a controlling method for a dryer according to oneexemplary embodiment may include turning the heat pump system on whenthe heat pump system and the heater are selected as the heat sources(S110), turning the heater on after the heat pump system is normallyturned on (S120), turning the heater off for cooling the drum toterminate the drying operation after the drying progresses (S140), andturning the heat pump system off after turning the heater off (S150).

Here, the method may further include running (working, starting,rotating) the drum by driving the driving motor before turning the heatpump system on (S90). The step of running the drum (S90) may beperformed by performing a reverse rotation and a forward rotation of thedriving motor in the sequential manner, and the step of turning the heatpump system may be started after performing a forward rotation of thedriving motor. From the perspective of the configuration, the drum isrun by the driving motor prior to turning the heat pump system on,thereby sequentially running loads.

FIGS. 10 and 11 show segmented steps of the load operation control forrunning those loads. As shown in FIGS. 10 and 11, the controlling methodfor the dryer may include running the drum by driving the driving motorfor the load operation control (S90), turning the heat pump system on bystarting the compressor (S110), and turning the heater on as the heatsource according to whether the compressor normally operates (S120).Here, FIG. 10 has omitted the step of turning on the heater (S120)because of the normal drying mode without using the heater.

The step of running the drum (S90) is performed by performing thereverse rotation and the forward rotation of the driving motor in thesequential manner for a predetermined time, and the step of turning theheat pump system on (S110) is started after forward rotation of thedriving motor.

In more detail, when starting the drying process, the controller firstruns (starts, initiates) the driving motor or the drum. Afterwards, thecontroller drives the compressor so as to turn the heat pump system on.

Upon running the drum, the controller reversely rotates and thenforwardly rotates the driving motor for a short time. This is to settension of a belt in the aspect of the characteristics of the hybriddryer having a belt-type driving force transfer system. This is also toprevent flowing of overcurrent at the beginning of driving the drivingmotor in view of the characteristic of the driving motor. Here, theforward rotation and the reverse rotation of the drum by the drivingmotor are defined because a specific direction is limited to the forwardrotation in the exemplary embodiment. Also, the ventilation fan in thisexemplary embodiment is implemented as a pull-type ventilation fan,which is present in a duct, through which air is exhausted out of thedrum, so as to suck the air discharged out of the drum toward theexhaust duct. Hence, it may be preferable to set the direction, in whichthe ventilation fan is rotated to suck the air toward the exhaust duct,as the forward rotation.

The steps shown in FIG. 10, may be performed in the normal drying mode,and the steps shown in FIG. 11 may be performed in the high-speed dryingmode. In FIG. 10, the compressor is started after the forward rotationof the driving motor and accordingly the heat pump system is turned on(S110). Here, the controller runs the compressor after the forwardrotation of the driving motor is performed for a predetermined time.This is to start the compressor after the ventilation fan is driven bydriving the driving motor so as for the heat pump system to be smoothlyrun.

However, a heater operation control may further be performed in thehigh-speed drying mode. In the high-speed drying mode, the dryer usesthe heater as well as the heat pump system as the heat sources. In thiscase, the controller may sense that the compressor is started andthereafter turn the heater on. This is to prevent an overload of thecompressor at the beginning of driving the compressor, which may becaused due to the heater being first turned on.

The heater operation control is protection means for ensuringreliability of the compressor in the high-speed drying mode. For this,the method may include determining whether the compressor included inthe heat pump system normally operates prior to turning the heater on(S121), and turning the heater on (S122). The step of turning the heateron (S122) may be performed after checking whether the heat pump systemnormally operates. The determining as to whether the compressor normallyoperates (S121) may be performed by comparing a temperature variation ofa refrigerant which has flowed through the compressor with a presetreference temperature variation.

In detail, the heater operation control may be applied when the heateras well as the heat pump system are selected as the heat sources forheating air supplied into the drum. The heater operation control mayinclude turning the heat pump system on (S110), and determining whetherthe compressor included in the heat pump system normally operates(S120). The heater operation control may be characterized in thatwhether to use the heater as the heat source is decided according towhether the compressor normally operates.

FIG. 12 shows an exemplary flowchart of the heater operation control. Asshown in FIG. 12, the step of turning the heat pump system on (S110)indicates starting the operation of the heat pump system of the heatsources in response to the drying operation being started. That is, asaforementioned, upon reception of a drying start command, the controllercontrols the driving motor to perform the reverse rotation and theforward rotation in the sequential manner, thereby starting thecompressor. Here, a temperature of a refrigerant at an outlet side ofthe compressor is first measured.

The determination as to whether the compressor included in the heat pumpsystem normally operates (S120) indicates determining whether thecompressor normally operates according to a temperature variation of arefrigerant which has passed through the compressor. Hence, the step ofmeasuring the temperature variation of the refrigerant having passedthrough the compressor (S121) may be performed.

That is, after running the compressor for a predetermined time, thecontroller remeasures the temperature of the refrigerant at the outletside of the compressor, thereby obtaining a temperature variation of therefrigerant. Here, when the obtained temperature variation of therefrigerant at the outlet side of the compressor is greater than apreset minimum difference value (or reference temperature variation),the controller determines that the compressor normally operates, therebyturning the heater on (S122).

On the contrary, when the measured temperature variation of therefrigerant at the outlet side of the compressor is smaller than thepreset reference temperature variation, there may be possibility thatthe compressor does not normally operate. Here, when the re-measuredtemperature of the refrigerant at the outlet side of the compressor ishigher than a lower limit of a reference operating temperature, it maycorrespond to the normal operation of the compressor. Therefore, thecontroller may turn the heater on. On the other hand, when there-measured temperature of the refrigerant at the outlet side of thecompressor is lower than the lower limit of the reference operatingtemperature, it may correspond to an erroneous (abnormal) operation ofthe compressor.

When the measured temperature variation of the refrigerant at the outletside of the compressor is smaller than the reference temperaturevariation, the controller may also first turn the heater on and thenre-measure the temperature of the refrigerant at the outlet side of thecompressor. Here, when the temperature variation of the refrigerant atthe outlet side of the compressor after turning the heater on is greaterthan the preset reference temperature variation, it corresponds to thenormal operation of the compressor, thereby performing the dryingoperation in the high-speed drying mode. Here, since the heater hasalready started, a separate control for turning the heater on is notnecessary.

However, when the temperature variation of the refrigerant at the outletside of the compressor after driving the heater is smaller than thepreset reference temperature variation, the controller turns the heateroff and forcibly converts the dryer into the normal drying mode, therebyperforming the drying operation.

As another exemplary embodiment different from the aforementioned, FIG.13 is a flowchart showing a process of initiating (starting, activating)a drying function by the controller in the dryer. As shown in FIG. 13,when needing to start a drying function, such as a user inputs a commandto perform the drying function through the manipulation panel, thecontroller may start the drying function according to a presetprocedure, such as rotating (running) the drum (S110 a).

Afterwards, to supply hot air into the drum, a current is applied to thecompressor to operate the compressor (S110 b), and then it is determinedwhether the compressor normally operates after applying the current tothe compressor (S120). If it is determined that the compressor is in anormal state, the heater is turned on (S120 c) and the drying functionis maintained. If not, the current applied to the compressor is blockedand a notification that an error occurs in the function of the dryer issent to the user via a display unit or the like disposed on themanipulation panel (S120 d).

As aforementioned, the dryer is the circulating type dryer in which theair exhausted from the drum is cooled and reheated to be resupplied intothe drum. In the circulating type dryer, the evaporator is used to coolair by receiving heat energy contained in the exhausted air to removemoisture contained the air and transfer the received heat energy to thecondenser to heat condensed air.

In the meantime, a refrigerant repetitively experiences a process inwhich the refrigerant transfers heat to air in the condenser, flows viathe evaporator and is compressed in the compressor. When heat is notsufficiently transferred to the air in the condenser, heat is notsufficiently absorbed in the evaporator and accordingly moisturecontained in the air is not sufficiently removed. Furthermore, arefrigerant of high temperature is introduced into the compressor, whichmay increase a load applied to the compressor. If the heat pump systemdoes not normally operate due to an error occurred in the compressor,heat transfer may not be normally happened in the condenser. Under thisstate, when the heater is turned on, the temperature of air exhausted isfurther raised, which results in an increase in the temperature of therefrigerant supplied into the compressor, thereby further deterioratingthe state of the compressor.

In other words, a maximum quantity of heat absorbable in the evaporatoris set to be equivalent to a quantity of heat exhausted from the drumwhen the condenser and the heater simultaneously operate. However, whenthe compressor does not normally operates or right after the compressoris started, the quantity of heat absorbable in the evaporator may notcome up to the maximum quantity of heat. When the compressor does notreach the normal state even if no error occurs therein, the quantity ofheat absorbable in the evaporator increases according to the lapse oftime, so the heater may be turned on. However, if an error has beengenerated, there may be much possibility of the absorbable quantity ofheat not increasing even if a time elapses. In this case, the compressorshould be turned off to be protected from damage caused due to anoverload.

Therefore, in the exemplary embodiment, before turning the heater onafter applying the current to the compressor, it may first be checkedwhether the compressor normally operates so as to address such problem.

Whether the compressor normally operates may be checked according tovarious methods. As one example, pressure of a refrigerant dischargedfrom the compressor may be sensed by a pressure sensor or the like so asto directly check whether or not an error has been generated. In theexemplary embodiment, whether or not the compressor normally operates isdetermined based on the temperature of the refrigerant. Detailed stepsthereof are shown in FIG. 14.

As shown in FIG. 14, after applying a current to the compressor (S110b), a temperature T1 of the refrigerant is measured by the refrigeranttemperature sensor after 10 seconds (S120 a). The temperature T2 of therefrigerant is re-measured after 60 seconds from the measurement of T1(S120 b). When the difference between the measured temperatures T1 andT2 exceeds 3.degree. C. (S120), it is determined that the compressor isnormally started and approaching its normal state (S120 c). If not, itis determined that an error has been generated in the compressor (S120d).

The exemplary embodiment shown in FIG. 13 may also be applied to a casewhere the operation of the compressor is performed for more than apredetermined time, as well as the beginning of running the compressor.That is, when the heater is needed to be turned on after a considerabletime has elapsed since the compressor was started, the heater is turnedon after checking whether or not the compressor normally operates.Accordingly, it may be checked whether or not heat generated in responseto the heater being run is absorbable in the evaporator, therebyprotecting the compressor.

For ensuring stability of the heat pump system even after normallyturning the heater on, the controlling method for the dryer may furtherinclude a compressor temperature control step (S131) of controlling thetemperature of the compressor. The compressor temperature control step(S131) may be performed to turn the heater on and off in a repetitivemanner according to the temperature of the refrigerant having passedthrough the compressor.

In the hybrid dryer having the heat pump system, when an overload occursin the compressor, it may result in lowering reliability of thecompressor, and causing damage on a target to be dried due to anincrease in inner temperature of the drum. Hence, the controllerperforms the compressor temperature control (S131) of controlling thetemperature of the refrigerant passing through the compressor forpreventing the overload of the compressor.

The exemplary embodiment of the compressor temperature control ischaracterized by repetitively turning on and off the heater or thecooling fan according to the temperature of the refrigerant havingpassed through the compressor. This is because a case of using both theheat pump system and the heater as the heat sources and a case of usingonly the heat pump system as the heat source are controlled in differentways.

Since the hybrid dryer has to continuously work the heat pump system,operation reliability of the compressor is important. Hence, formaintaining the reliability of the compressor, when the overload occursin the compressor, the dryer may have a serious problem mechanically orduring the drying operation. To address the problem, a valve control ofprotecting reliability of the compressor (S132) is needed.

The valve control may differ in the normal drying mode and thehigh-speed drying mode. Each drying mode uses a different heat sourceand exhibits different heat load, so the control by the controller maydiffer.

According to the valve control, to prevent an overload of the heat pumpsystem, when a temperature of a refrigerant, which is measured while theheater is turned off, exceeds an upper limit of the temperature range orfails to reach a lower limit of the temperature range within apredetermined time, the controller may control an opening rate of theexpansion valve disposed in the heat pump system.

A drum temperature control of controlling the temperature of the drumafter the heater is turned on (S133) may further be performed. In thedrum temperature control step (S133), the heater is turned on and off ina repetitive manner according to temperature of air supplied into thedrum or temperature of air discharged from the drum, and when the numberof turning the heater off reaches a predetermined reference number oftimes, only the heat pump system is used as the heat source to controlthe dryer to be converted into the normal drying mode.

In the meantime, when heat supply by the heat source is not neededbecause a target to be dried is dried up to an appropriate dryness, acooling process of cooling the target to be dried such that the targetto be dried can have humidity and temperature as appropriate as a userbeing able to immediately wear it by taking out of the dryer.

The operation of the heat sources is stopped during the cooling process.The stopping of the operation of the heat source may be performedsequentially by turning the heater off (S150) and turning the heat pumpsystem off (S160).

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A dryer capable of drying objects to be dried,the dryer comprising: a main body; a drum rotatably installed inside themain body to accommodate objects to be dried therein; a drive motor todrive the drum; a first fan to blow air into the drum; a heat pumpsystem to heat air supplied into the drum, wherein the heat pump systemincludes an evaporator disposed at an air outlet side of the drum, afirst condenser disposed at an air inlet side of the drum, an expansionvalve, and a compressor; a heater installed between the drum and thefirst condenser to heat air supplied into the drum; a first sensor tomeasure a temperature of a refrigerant circulating in the heat pumpsystem; a second condenser to overcool a refrigerant supplied into theexpansion valve; a second fan to supply external air into the main bodyto cool the second condenser or the compressor; and a controller thatcontrols at least one of the compressor, the expansion valve, theheater, the first fan, or the second fan based on a temperature measuredby the first sensor.
 2. The dryer of claim 1, wherein the dryercomprises a circulation channel, the circulation channel being formedwith a connection between a first flow path of air supplied into thedrum and a second flow path of air discharged from the drum.
 3. Thedryer of claim 1, wherein the controller controls the at least one ofthe compressor, the expansion valve, the heater, the first fan, or thesecond fan according to a user selection input through a control panel.4. The dryer of claim 3, wherein the controller turns on only the heatpump system, but not the heater according to the input user selection toimprove energy efficiency.
 5. The dryer of claim 3, wherein thecontroller turns on the heat pump system and the heater according to theinput user selection to reduce a drying time.
 6. The dryer of claim 3,wherein the controller controls the heater according to the input userselection to protect objects to be dried from damage caused by hot air.7. The dryer of claim 1, wherein the dryer further comprises a secondsensor configured to measure a temperature of air circulating throughthe drum, wherein the controller turns the heater on and off in arepetitive manner based on the temperature measured by the second sensoraccording to a user selection input through a control panel, to protectthe objects to be dried from damage caused by hot air.
 8. The dryer ofclaim 1, wherein the controller turns the heater on and off in arepetitive based on at least one of a temperature of a refrigerant at aninlet side of the compressor or a temperature of a refrigerant at anoutlet side of the compressor.
 9. The dryer of claim 1, wherein thecontroller controls an opening rate of the expansion valve based on atleast one of a temperature of a refrigerant at an inlet side of thecompressor or a temperature of a refrigerant at an outlet side of thecompressor.
 10. The dryer of claim 1, wherein the controller turns thesecond fan on and off in a repetitive manner based on at least one of atemperature of a refrigerant at an inlet side of the compressor or atemperature of a refrigerant at an outlet side of the compressor. 11.The dryer of claim 1, wherein the controller turns the second fan on andoff in a repetitive manner based on at least one of a temperature of arefrigerant at an inlet side of the evaporator or a temperature of arefrigerant at an outlet side of the evaporator.
 12. A dryer capable ofdrying objects to be dried, the dryer comprising: a main body; a drumrotatably installed inside the main body to accommodate objects to bedried therein; a drive motor to drive the drum; a first fan to blow airinto the drum; a heat pump system to heat air supplied into the drum,wherein the heat pump system includes an evaporator disposed at an airoutlet side of the drum, a first condenser disposed at an air inlet sideof the drum, an expansion valve, and a compressor; a heater installedbetween the drum and the first condenser to heat air supplied into thedrum; a first sensor configured to measure a temperature of aircirculating through the drum; a second sensor to measure a temperatureof a refrigerant circulating in the heat pump system; a second condenserto overcool a refrigerant supplied into the expansion valve; a secondfan to supply external air into the main body to cool the secondcondenser or the compressor; and a controller that controls at least oneof the compressor, the expansion valve, the heater, the first fan, orthe second fan based on temperatures measured by the first sensor andthe second sensor.
 13. A method for a controlling dryer capable ofdrying objects to be dried, wherein the dryer comprises a main body, adrum rotatably installed inside the main body to accommodating objectsto be dried therein, a drive motor to drive the drum, a first fan toblow air into the drum, a heat pump system to heat air supplied into thedrum, wherein the heat pump system includes an evaporator disposed at anair outlet side of the drum, a first condenser disposed at an air inletside of the drum, an expansion valve, and a compressor, a heaterinstalled between the drum and the first condenser to heat air suppliedinto the drum, a first sensor to measure a temperature of a refrigerantcirculating in the heat pump system, a second condenser to overcool arefrigerant supplied into the expansion valve, and a second fan tosupply external air into the main body to cool the second condenser orthe compressor, the method comprising: receiving a user selection inputthrough a control panel; and controlling via a controller at least oneof the compressor, the expansion valve, the heater, the first fan, orthe second fan based on a temperature measured by the first sensor. 14.The method of claim 13, wherein if the received user selection is toimprove energy efficiency, the controlling turns on the heat pumpsystem, but not the heater.
 15. The method of claim 13, wherein if thereceived user selection is to reduce a drying time, the controllingturns on the heat pump system and the heater.
 16. The method of claim13, wherein if the received user selection is to protect the objects tobe dried from damage caused by hot air, the controlling controls theheater to protect the objects to be dried from damage caused by hot air.17. The method of claim 16, wherein the controlling comprising turningthe heater on and off in a repetitive manner based on a temperaturemeasured by a second sensor, wherein the second sensor measures atemperature of air circulating through the drum.
 18. The method of claim13, wherein the controlling comprises controlling at least one of anexpansion valve based on at least one of a temperature of a refrigerantat an inlet side of the compressor or a temperature of a refrigerant atan outlet side of the compressor.
 19. The method of claim 13, whereinthe controlling comprises turning the second fan on and off in arepetitive manner based on at least one of a temperature of arefrigerant at an inlet side of the compressor or a temperature of arefrigerant at an outlet side of the compressor.
 20. A method for acontrolling dryer capable of drying objects to be dried, wherein thedryer comprises a main body, a drum rotatably installed inside the mainbody to accommodating objects to be dried therein, a drive motor todrive the drum, a first fan to blow air into the drum, a heat pumpsystem to heat air supplied into the drum, wherein the heat pump systemincludes an evaporator disposed at an air outlet side of the drum, afirst condenser disposed at an air inlet side of the drum, an expansionvalve, and a compressor, a heater installed between the drum and thefirst condenser to heat air supplied into the drum, a first sensorconfigured to measure a temperature of air circulating though the drum,and a second sensor to measure a temperature of a refrigerantcirculating in the heat pump system, a second condenser to overcool arefrigerant supplied into the expansion valve, and a second fan tosupply external air into the main body to cool the second condenser orthe compressor, the method comprising: receiving a user selection inputthrough a control panel; and controlling via a controller at least oneof the compressor, the expansion valve, the heater, the first fan, orthe second fan based on temperatures measured by the first sensor andthe second sensor.
 21. Apparatus for a controlling dryer capable ofdrying objects to be dried, wherein the dryer comprises a main body, adrum rotatably installed inside the main body to accommodating objectsto be dried therein, a drive motor to drive the drum, a first fan toblow air into the drum, a heat pump system to heat air supplied into thedrum, wherein the heat pump system includes an evaporator disposed at anair outlet side of the drum, a first condenser disposed at an air inletside of the drum, an expansion valve, and a compressor, a heaterinstalled between the drum and the first condenser to heat air suppliedinto the drum, a first sensor to measure a temperature of a refrigerantcirculating in the heat pump system, a second condenser to overcool arefrigerant supplied into the expansion valve, and a second fan tosupply external air into the main body to cool the second condenser orthe compressor, the method comprising: means for receiving a userselection; and means for controlling at least one of the compressor, theexpansion valve, the heater, the first fan, or the second fan based on atemperature measured by the first sensor.
 22. Apparatus for acontrolling dryer capable of drying objects to be dried, wherein thedryer comprises a main body, a drum rotatably installed inside the mainbody to accommodating objects to be dried therein, a drive motor todrive the drum, a first fan to blow air into the drum, a heat pumpsystem to heat air supplied into the drum, wherein the heat pump systemincludes an evaporator disposed at an air outlet side of the drum, afirst condenser disposed at an air inlet side of the drum, an expansionvalve, and a compressor, a heater installed between the drum and thefirst condenser to heat air supplied into the drum, a first sensorconfigured to measure a temperature of air circulating though the drum,and a second sensor to measure a temperature of a refrigerantcirculating in the heat pump system, a second condenser to overcool arefrigerant supplied into the expansion valve, and a second fan tosupply external air into the main body to cool the second condenser orthe compressor, the method comprising: means for receiving a userselection; and means for controlling at least one of the compressor, theexpansion valve, the heater, the first fan, or the second fan based ontemperatures measured by the first sensor and the second sensor.